net/rds/page.c

   1 /*
   2  * Copyright (c) 2006 Oracle.  All rights reserved.
   3  *
   4  * This software is available to you under a choice of one of two
   5  * licenses.  You may choose to be licensed under the terms of the GNU
   6  * General Public License (GPL) Version 2, available from the file
   7  * COPYING in the main directory of this source tree, or the
   8  * OpenIB.org BSD license below:
   9  *
  10  *     Redistribution and use in source and binary forms, with or
  11  *     without modification, are permitted provided that the following
  12  *     conditions are met:
  13  *
  14  *      - Redistributions of source code must retain the above
  15  *        copyright notice, this list of conditions and the following
  16  *        disclaimer.
  17  *
  18  *      - Redistributions in binary form must reproduce the above
  19  *        copyright notice, this list of conditions and the following
  20  *        disclaimer in the documentation and/or other materials
  21  *        provided with the distribution.
  22  *
  23  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
  24  * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
  25  * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
  26  * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS
  27  * BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
  28  * ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
  29  * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
  30  * SOFTWARE.
  31  *
  32  */
  33 #include <linux/highmem.h>
  34 #include <linux/gfp.h>
  35 #include <linux/cpu.h>
  36 #include <linux/export.h>
  37
  38 #include "rds.h"
  39
  40 struct rds_page_remainder {
  41         struct page     *r_page;
  42         unsigned long   r_offset;
  43 };
  44
  45 static
  46 DEFINE_PER_CPU_SHARED_ALIGNED(struct rds_page_remainder, rds_page_remainders);
  47
  48 /*
  49  * returns 0 on success or -errno on failure.
  50  *
  51  * We don't have to worry about flush_dcache_page() as this only works
  52  * with private pages.  If, say, we were to do directed receive to pinned
  53  * user pages we'd have to worry more about cache coherence.  (Though
  54  * the flush_dcache_page() in get_user_pages() would probably be enough).
  55  */
  56 int rds_page_copy_user(struct page *page, unsigned long offset,
  57                        void __user *ptr, unsigned long bytes,
  58                        int to_user)
  59 {
  60         unsigned long ret;
  61         void *addr;
  62
  63         addr = kmap(page);
  64         if (to_user) {
  65                 rds_stats_add(s_copy_to_user, bytes);
  66                 ret = copy_to_user(ptr, addr + offset, bytes);
  67         } else {
  68                 rds_stats_add(s_copy_from_user, bytes);
  69                 ret = copy_from_user(addr + offset, ptr, bytes);
  70         }
  71         kunmap(page);
  72
  73         return ret ? -EFAULT : 0;
  74 }
  75 EXPORT_SYMBOL_GPL(rds_page_copy_user);
  76
  77 /**
  78  * rds_page_remainder_alloc - build up regions of a message.
  79  *
  80  * @scat: Scatter list for message
  81  * @bytes: the number of bytes needed.
  82  * @gfp: the waiting behaviour of the allocation
  83  *
  84  * @gfp is always ored with __GFP_HIGHMEM.  Callers must be prepared to
  85  * kmap the pages, etc.
  86  *
  87  * If @bytes is at least a full page then this just returns a page from
  88  * alloc_page().
  89  *
  90  * If @bytes is a partial page then this stores the unused region of the
  91  * page in a per-cpu structure.  Future partial-page allocations may be
  92  * satisfied from that cached region.  This lets us waste less memory on
  93  * small allocations with minimal complexity.  It works because the transmit
  94  * path passes read-only page regions down to devices.  They hold a page
  95  * reference until they are done with the region.
  96  */
  97 int rds_page_remainder_alloc(struct scatterlist *scat, unsigned long bytes,
  98                              gfp_t gfp)
  99 {
 100         struct rds_page_remainder *rem;
 101         unsigned long flags;
 102         struct page *page;
 103         int ret;
 104
 105         gfp |= __GFP_HIGHMEM;
 106
 107         /* jump straight to allocation if we're trying for a huge page */
 108         if (bytes >= PAGE_SIZE) {
 109                 page = alloc_page(gfp);
 110                 if (!page) {
 111                         ret = -ENOMEM;
 112                 } else {
 113                         sg_set_page(scat, page, PAGE_SIZE, 0);
 114                         ret = 0;
 115                 }
 116                 goto out;
 117         }
 118
 119         rem = &per_cpu(rds_page_remainders, get_cpu());
 120         local_irq_save(flags);
 121
 122         while (1) {
 123                 /* avoid a tiny region getting stuck by tossing it */
 124                 if (rem->r_page && bytes > (PAGE_SIZE - rem->r_offset)) {
 125                         rds_stats_inc(s_page_remainder_miss);
 126                         __free_page(rem->r_page);
 127                         rem->r_page = NULL;
 128                 }
 129
 130                 /* hand out a fragment from the cached page */
 131                 if (rem->r_page && bytes <= (PAGE_SIZE - rem->r_offset)) {
 132                         sg_set_page(scat, rem->r_page, bytes, rem->r_offset);
 133                         get_page(sg_page(scat));
 134
 135                         if (rem->r_offset != 0)
 136                                 rds_stats_inc(s_page_remainder_hit);
 137
 138                         rem->r_offset += ALIGN(bytes, 8);
 139                         if (rem->r_offset >= PAGE_SIZE) {
 140                                 __free_page(rem->r_page);
 141                                 rem->r_page = NULL;
 142                         }
 143                         ret = 0;
 144                         break;
 145                 }
 146
 147                 /* alloc if there is nothing for us to use */
 148                 local_irq_restore(flags);
 149                 put_cpu();
 150
 151                 page = alloc_page(gfp);
 152
 153                 rem = &per_cpu(rds_page_remainders, get_cpu());
 154                 local_irq_save(flags);
 155
 156                 if (!page) {
 157                         ret = -ENOMEM;
 158                         break;
 159                 }
 160
 161                 /* did someone race to fill the remainder before us? */
 162                 if (rem->r_page) {
 163                         __free_page(page);
 164                         continue;
 165                 }
 166
 167                 /* otherwise install our page and loop around to alloc */
 168                 rem->r_page = page;
 169                 rem->r_offset = 0;
 170         }
 171
 172         local_irq_restore(flags);
 173         put_cpu();
 174 out:
 175         rdsdebug("bytes %lu ret %d %p %u %u\n", bytes, ret,
 176                  ret ? NULL : sg_page(scat), ret ? 0 : scat->offset,
 177                  ret ? 0 : scat->length);
 178         return ret;
 179 }
 180 EXPORT_SYMBOL_GPL(rds_page_remainder_alloc);
 181
 182 void rds_page_exit(void)
 183 {
 184         unsigned int cpu;
 185
 186         for_each_possible_cpu(cpu) {
 187                 struct rds_page_remainder *rem;
 188
 189                 rem = &per_cpu(rds_page_remainders, cpu);
 190                 rdsdebug("cpu %u\n", cpu);
 191
 192                 if (rem->r_page)
 193                         __free_page(rem->r_page);
 194                 rem->r_page = NULL;
 195         }
 196 }